Rock drill



W. A. SMITH, SR

Rocx DRILL June 13, 1939.

Filed Oct. 19, 1937 H IS ATTORNEY,

Patented June 13, 1939 UNITED STATES PATENT OFFICE ROCK D'RILL Application October 19, 1937, Serial No. 169,772

3 Claims.

This invention relates to rock drills, and more particularly to valve mechanism controlling the admission of pressure fluid to a percussive element of a fluid actuated rock drill.

5 It is an object of the present invention to obtain a heavy blow of the percussive element against the working implement.

Another object is to utilize the pressure fluid expansively for actuating the percussive element and, therefore, to reduce to a minimum the power cost of operating the drill.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is a longitudinal view, in section, of a rock drill constructed in accordance with the practice of the invention, and

Figures 2 and 3 are perspective views of details.

Referring more particularly to the drawing, 20 designates a rock drill comprising a cylinder 2| and a back head 22 which may be attached to the cylinder in any well known manner.

The cylinder 2| is bored to provide a piston chamber 23 having a closure 24 at its front end and the rear end of the piston chamber is closed, in the present instance, by a valve mechanism designated in its entirety by 25. The piston chamber 23 has a free exhaust port 26 and contains a reciprocatory hammer piston 21 which controls the exhaust port 26 and has a front reduced stem 28 extending slidably through the closure 24.

The valve mechanism is arranged in an enlarged bore 29 in the rear end of the cylinder 2|. It includes a bushing 30 which acts as a bearing for a rifle bar 3| wherewith the piston 21 may be slidably interlocked. The rifle bar has the usual head 32 which carries pawls 33 adapted to engage teeth 34, of a ratchet ring 35 encircling the head 32 and encased by the back head 22, for determining the direction of rota- 5 tion of the rifle bar and thus of the piston 21.

The back head 22 is centralized with respect to the cylinder 2| by a plate 36 extending into the adjacent ends of these elements and bearing against the rearward end of the bushing 30 50 and the front end of the ratchet ring 35. In the side of the back head 22 is a throttle valve 31 of the rotary type whereby the admission of pressure fluid into the rock drill is controlled. The throttle valve has a central aperture 38 which 5 may be in constant communication with a source of pressure fluid. In its wall is a port 39 to register with a passage 40 in the ratchet ring 35 and the plate 36 and leading to a chamber 4| in the front end of the plate 35.

The valve mechanism 25 to which the inven- 5 tion is applied is of the type illustrated in United States Patent No. 2,048,957 granted to W. A. Smith, Sr., et al., July 28, 1936. It accordingly comprises a valve chest consisting of a series of plates 42, 43, 44 and of which the latter 10 may be an integral portion of the bushing 30 and its outer portion lies between the plates 44 and 36. The plate 42 is the foremost portion of the valve chest and forms a closure for the rear end of the piston chamber 23. The plates 5 43 and 44 are interposed between the plates 42 and 45 and the various plates are so formed as to enable adjacent plates to be in telescopic engagement with each other.

The plates 43 and 44, forming the interme- 20 diate portion of the valve chest, are in the form of rings and their inner surfaces cooperate with the peripheral surface of the bushing 30 to define a valve chamber 46 of annular shape to accommodate a valve 41 whereby pressure fluid 5 is distributed to the ends of the piston chamber 23. The valve 41 is, therefore, also of annular shape and is guided by the bushing 30 and the plates 43 and 44. On the periphery of the valve is a flange 48 of which the front and rear ends 30 constitute actuating surfaces 49 and 50, respectively, which are alternately subjected to pressure fluid for actuating the valve.

The pressure fluid employed for this purpose is conveyed to the actuating surfaces by kicker 35 passages 5| and 52 leading from the piston chamber 23 to the actuating surfaces 49 and 50, respectively. The kicker passages are crossed. That designated 5| opens into the piston chamber forwardly of the exhaust port 26 40 and the passage 52 opens into the piston chamber rearwardly of the exhaust port, preferably closely adjacent thereto so that pressure fluid is admitted into the kicker passages from the piston chamber immediately before the piston 45 uncovers the exhaust port.

Intermediate the ends of the valve 41 and in its inner surface is a supply chamber 53 into which pressure fluid is introduced by passages 54 in the bushing 30 and leading from the supply chamber 4|. In the portions of the valve lying forwardly and rearwardly of the chamber 53 are passages 55 and 56, respectively, through which the pressure fluid passes for charging the ends of the piston chamber. The passages 55 5,5.

and 56 have their outlet openings in the ends of the valve so that during its course to the piston chamber the pressure fluid flows across the ends of the valve of which the front end designated 51 constitutes a holding surface and the rear end a holding surface 58. The holding surfaces are coextensive with the ends of the valve and are subjected to the pressure fluid flowing to the inlet passages for holding the valve in its limiting'positions.

In the respects set forth the valve is substantially like that disclosed in the aforesaid patent. It differs therefrom, however, in

that it includes means for, effecting the cut-off to'both ends of the piston chamber during a portion of the movement of the valve in order pthat the pressure fluid may act 'expansively against the piston for impelling it throughout a portion of its stroke. The valve chest is accordingly provided with a ring 59 arranged about a boss 60 on the bushing adjacent the plate The ring 59 may be press fitted, or otherwise fixedly secured, to the boss 60 and its forward portion lies below the boss and cooperates with the bushing 39 to define an annular-groove 5! into. which thevalve end extends in the rear- 'most'limiting position of the valve. The'bottom 'off the groove'sl oonstitutes a seating surface 62 5 for the end of the valveand cooperates therewith to prevent leakage of pressure fluid from the passages 56 in the seated position of the valve. V

The portion of the ring 59 lying below the boss 69 is of such length that when the valve 41 occupies its foremost limiting position a substantial flow area will exist between the rear end of the valve and the ring 59 to permit the free flow of pressure fluid from the passages 55 to an inlet passage 63 leading from the rear end of .the valve chamber 46 to the front end of the piston chamber 23.-

Means are likewise provided at the opposite end of the valve chamber to cooperate with the peripheral surface of the end of the valve for preventing the flow of pressure fluid tothe piston chamber during a portion of the stroke of the valve. The plate 42 is accordingly provided-with a depression 64, of cylindrical shape, of which the side surface 65 engages the periphery of the valve to prevent the flow of pressure fluid in an' outwardly direction until the valve has moved out of the plane of the plate 42.

The depression 64 is of greater depth than is required to accommodate the endof the valve and in the bottomi of the depression is a plate 66. The plate 66 may be affixed to the plate 42 in any suitable manner and has a boss 61 of which the peripheral surface 68 is ground to fit the inner surface of the valve and cooperates with the surface to define an annular groove enter the rear end of the piston chamber. These paths or inlet passages designated H and I2 lie respectively in planes outside and-inside of the 7 plane ofv the valve. "In the construction shown the passages H are located in the' plate 42, and

mechanism,

The distance between the confronting surfaces of the ring 59 and the plate 42 is slightly less than the length of the valve 41 so that during the intermediate portion of the valve stroke the side surfaces of thegrooves BI and 69 will be simultaneously partly overlapped by the valve.

' In this way the flow of pressure fluid will be m'omentarily cut-off to both ends of the cylinder during the time the piston is passing through the intermediate portion of the piston chamber 23. The pressure fluid actuating the piston may, therefore, act expansively, the piston may deliver a powerful blow against the working implement since no pressure fluid may enter the piston chamber in advance of the piston to cushion its blow, and the active end of the piston chamber will be cut-01f from pressure fluid supply before the piston uncovers the exhaust port 25. V

The described structure making the aforesaid advantages possible may be cheaply and practicably produced since the surfaces relied upon for effecting the cut-off of pressure fluid to the piston chamber are each formed on different plates and may, for that reason, be ground to the precise dimensions essential'to the efficient operation of the" valve. The portions of the valve, namely, the surfaces 51 and 58 over which the pressure fluid flows during its course to the piston chamber may, moreover, be used as seating surfaces which by their repeated striking against the surfaces 10 and 62 will be beaten into and constantly maintained in a nicely polished and true sealing condition, thereby correcting such damage as may be occasioned by the abrasive action of solids entrained in the pressure fluid flowing over the ends of the valve.

I claim:

1. In a fluid actuated rock drill, the combination of a cylinder and a piston, a valve chest having a valve chamber, inlet passages leading from the valve chamber tothe cylinder, an annular valve reciprocable inthe valve chamber to control the flow of pressurefluid to the inlet passagesand having seating surfaces on its ends, seats at the ends of the valve chamber for the seating surfaces of the valve, and means adjacent one seat cooperating with the inner and outer surfaces of the valve to out off the flow of pressure fluid to an end of the cylinder during a portion of "the movement of; the valve. 7

2. In a fluid actuated rock drill, the combination of a cylinder and a piston, a valve chest having. a valve chamber, inlet'passages leading from the valve chamber to the cylinder, an annular valve recipr'ocable in the valve chamber to control the flow of pressure fluid to the inlet passages and having seating-surfaces on its ends, a pair of plates arranged one within another and oneof said'plates forming a seat for one of the seating surfaces, and cylindrical surfaces on the plates cooperating with the inner and outer surof the movement of the valve. r

3. In a fluid actuated rock drill, the combination of a cylinder and a piston, a valve chest having a valve chamber, an annular reciprocatory valve in the valve chamber having a plurality of channels through which pressure fluid flows for charging the cylinder, seating surfaces on the ends of the valve, an inlet passage for conveying pressure fluid from the valve chamber to one end of the cylinder, a pair of plates arranged 10 one within another and one of said plates forming a seat for one of the seating surfaces, inlet passages in the plates arranged on opposite sides of the channels to convey pressure fluid to the other end of the cylinder, and cylindrical surfaces on the plates cooperating with the inner and outer surfaces of the valve to cut off the flow of pressure fluid to the last said inlet passages during a portion of the movement of the valve.

WILLIAM A. SMITH, SR. 

